/*
 * @Author: lixiaowei
 * @Date: 2021-04-09 12:45:39
 * @LastEditors: lixiaowei
 * @LastEditTime: 2021-04-09 12:46:50
 * @Description: 递推过程
 * @FilePath: /heima-bli/泛型编程/demo2.cpp
 */
#include <iostream>
using namespace std;

// 1+2+3...+100 => n*(n+1)/2